ISSN Online: 2377-424X
International Heat Transfer Conference 12
Local heat/mass transfer characteristics in a square duct with various rib arrangements
Resumo
The present study investigates the effects of rib arrangements and gap positions on the rib on local heat/mass
transfer in a duct. The combined effects of the gap flows of the discrete ribs and the secondary flows are
examined for the purpose of the promotion of the uniformity of heat/mass transfer distributions as well as the
augmentation of heat/mass transfer. A square channel with rectangular ribs is used for the stationary duct test.
The rib-to-rib pitch to the rib height ratio of 8, and the rib attack angle of 60 deg. The gap width is 5 mm and two
gap positions, which are upstream and downstream gaps, are examined. A naphthalene sublimation method is
used to measure local heat/mass transfer coefficients. A complex flow structure occurs in the cooling passage
with rib turbulators that promote heat transfer on the wall. Therefore, a numerical computation is performed
using a commercial code to calculate the flow structures. The parallel rib arrangements make a pair of counter
rotating secondary flows in the cross section, while the cross rib arrangements make a single rotating secondary
flow including small vortices. These secondary flow patterns affect significantly the heat/mass transfer on the
ribbed wall. Though the gap flow of the discrete ribs is relatively weaker than the rib-induced secondary flow, it
promotes local turbulence and flow mixing near the ribbed wall.